Overview of experimental research on breakdown in liquid dielectrics under nanosecond pulse

The breakdown properties of liquid dielectric are easily influenced by experimental conditions, so that to this day no one theory can explain all experimental observations. The paper introduces experimental development a-bout study of liquid dielectric breakdown properties of different voltage polarity and wave shape, of changing environmental pressure around liquid etc, presents different experimental technique collecting electrics with optics, shows some important fruits of experiential formula and breakdown mechanisms, reviews excellencies and disadvantages of plane-plane, point-plane, sphere-plane electrodes etc. Polariization effect of breakdown of point-plane electrodes infers different breakdown mechanisms of positive and negative streamers of liquid dielectric. The breakdown properties of single nanosecond impulse voltage are characteristic of less voltage operative time and corresponding higher breakdown voltage. It is opposite to breakdown properties of repetitive impulses which take on low breakdown voltage as a result of cumulative affection of polarization of liquid dielectric under applied repetitive impulses. Both single and repetitive impulses reveal the essential characteristics of liquid breakdown. So far the optic observation of streamer imaging mainly includes shadow imaging, schlieren imaging, Kerr effect, image converter camera etc. among these kinds of methods image converter camera is only one which can be used to observe liquid breakdown under nanosecond impulse voltage. The breakdown properties of liquid dielectric are easily influenced by experimental conditions, so that to this day no theory can explain all experimental observations. The breakdown voltage under repetitive impulses shows very notable separation in a large range, which is explored in detail.